1482 Part IX / Diseases of the Nervous System
The Conscious Recall of Memories Is a
Creative Process
For most of us, memory is the conscious imaginative
reliving of a past experience. If we take no account of
subjective experience (the behaviorist stance), however,
memory is a process by which our past experience alters
future behavior. Our behavior is often affected by past
experience, but without conscious recall of the memory
or awareness of the influence it is having on us. Once
again, this type of experience is seen most strikingly in
patients with damage to specific areas of the brain.
Some patients become densely amnesic after dam-
age to the medial regions of the temporal lobe. They
show no decline in intellect as measured by IQ tests
but cannot remember anything for more than a few
minutes. Although devastating, this memory impair-
ment is actually rather circumscribed. The problem
is largely manifested in declarative memory, and most
severely in a type of declarative memory called epi-
sodic memory, the ability to recollect events in one’s life
(Chapter 54). Procedural memory, in which conscious-
ness has a minor role (Chapter 53), remains intact.
Thus, patients can still remember motor skills such as
riding a bicycle and can often learn new motor skills
at a normal rate. This selective effect of brain damage
can lead to dramatic dissociations. A patient who has
been learning some new skill every day for a week will
deny ever having performed the task before. He is then
surprised to find how skillful he has become.
A widely used protocol tests subjects’ ability to
recall lists of words they have memorized, a task that
taps a form of declarative memory. In the recall phase,
a subject is presented with a list of the words that were
on the study list plus new words. An amnesic patient
has great difficulty with this type of task and may
misclassify most of the previously seen words as new
since she cannot recall seeing them before. Neverthe-
less, the brain activity elicited by reading old words is
different from that elicited by the new words: There is
unconscious recognition of a difference, equivalent to
that shown by patients with unilateral neglect or pros-
opagnosia. Normal subjects usually find this task easy,
but they too will occasionally misclassify old words
as new; as with amnesiacs, evoked brain responses
in normal subjects register the distinction lost to con-
scious recall (Figure 59–9).
Occasionally, a subject misclassifies a new word as
an old one. This misclassification amounts to a false
memory. Such misclassifications are most likely to
occur when the new word is semantically related to
one or more of the old words. If the list of old words
contained big, great, huge, then the new word large is
Figure 59–9 Brain activity shows the imprint of forgotten
memories.Subjects were presented with a list of words,
including some that had been presented earlier and some that
were new. When asked to identify the words presented earlier,
subjects correctly identified some of the old words but forgot
others. Immediately after the visual presentation of a word,
there is a brief fluctuation in the evoked potential in the brain.
Evoked responses in the parietal region of the brain reflect
whether or not the words had been seen before, even when
subjects did not consciously recognize the words. The pattern
produced by old words, whether recognized or not, is different
from that produced by the new words. (Reproduced, with permis-
sion, from Rugg et al. 1998. Copyright © 1998 Springer Nature.)
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likely to be identified as old. One explanation for this
is that the perception of the new word large has been
unconsciously primed by the previous presentation of
the old words. Thus, the new word large is processed
easily and quickly, and because the subject is aware of
this, he concludes the word must be familiar and clas-
sifies it as old.
This observation emphasizes that memory is a
creative process. Our conscious memories are con-
structed from both conscious recall and unconscious
knowledge. To guard against false memories, as with
false percepts, we use our knowledge about the world
to determine which memories are plausible.
In some patients, the process by which memories
are screened can become dramatically disturbed. If asked
what happened yesterday, most patients with amne-
sia will say that they cannot remember, but a few will
give elaborate accounts that do not correspond to real-
ity. Such false memories are called confabulations and can
sometimes be extremely implausible. For example,
one patient said that he had met Harold Wilson
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